1. Field of the Invention
The present invention relates to a small, light-weight microwave and millimeter wave device which is suitable for mass production and has good high frequency characteristics.
2. Description of the Related Art
In recent years, as the processing speed of a data processing device and the resolution of an image processing device have increased, a high-speed, large-capacity personal communication apparatus using a high frequency wave such as a microwave or a millimeter wave has attracted public attention. As a microwave and millimeter wave device in such a communication apparatus, a module has been actively developed in which a high frequency semiconductor chip is mounted directly on a dielectric substrate having transmission lines thereon. As higher frequencies have been used, a flip-chip mounting method has attracted particular public attention, by which the semiconductor chip is connected onto the dielectric substrate via metal bumps.
FIG. 21 is a schematic diagram illustrating an HMIC 5100 Hybrid Microwave Integrated Circuit) as an exemplary microwave and millimeter wave device. FIG. 21B is a cross-sectional view of the HMIC 5100 taken along line 21A-21B in FIG. 21A.
The HMIC 5100 includes a single transistor chip 211, a dielectric substrate 212 on which passive circuits 5150 in FIG. 21A have been formed by transmission lines, and metal bumps 213 in FIG. 21B. The single transistor chip 211 and the dielectric substrate 212 are attached together, with the respective surface sides facing each other, so that electrodes on the single transistor chip 211 are physically and electrically connected to signal lines 214 and grounding conductor portions 215 on the dielectric substrate 212 via the metal bumps 213. The grounding conductor portions 215 on the surface side of the dielectric substrate 212 are connected to a rounding conductor surface 217 in FIG. B on the reeves side of the dielectric substrate 212 via through holes 216. A DC out capacitor 218, a radial stub 219, a chip resistor 220, a chip capacitor 221, and the like, are formed on the surface side of the dielectric substrate 212 as the passive circuits 5150.
An example of such an HMIC technique is described in 1997 IEEE MTT-S digest, pp. 447-450.
Another such technique is a flip-chip mounting technique of an MMIC (Monolithic Microwave Integrated Circuit) onto the dielectric substrate 212. The MMIC includes an active element such as a transistor and passive elements such as a transmission line, a spiral inductor and a thin film capacitor provided on the same semiconductor chip, thereby implementing functional blocks, such as an amplifier, a mixer and an oscillator, on the semiconductor chip. FIG. 22A illustrates an exemplary MMIC 222 being flip-chip mounted on the dielectric substrate 212, and FIG. 22B is a cross-sectional view taken along line 22A-22B in FIG. 22A.
The illustrated flip-chip structure includes the MMIC 222, the dielectric substrate 212 including transmission lines provided thereon, and the meal bumps 213. The dielectric substrate 212 including transmission lines provided thereon, and the metal bumps 213. The dielectric substrate 212 and the MMIC 222 are attached together, with the respective surface sides acing each other, so that electrodes provided along the periphery of the MMIC 222 are physically and electrically connected to signal lines 224 and the grounding conductor portions 215 on the dielectric substrate 212 via the metal bumps 213. The grounding conductor portions 215 on the surface side of the dielectric substrate 212 are connected to the grounding conductor surface 217 in FIGS. 21B on the reverse side of the dielectric substrate 212 via the through holes 216.
An exemplary MMIC flip=chip technique is described in 1994 IEEE MTT-S digest, pp. 1707-1710.
However, the conventional techniques have the following problems.
For HMIC, the first problem is that the semiconductor chips as the single active elements have to be mounted one by one, thus resulting in a high production cost. The second problem is that the semiconductor chip as the single active element is very small in size, and thus is difficult to handle. As a result, variation in the high frequency characteristics is likely to occur due to misalignment between the individual active elements and the substrate. The third problem is that the number of metal bumps which can be mounted on one semiconductor chip is limited, thereby resulting in an insufficient mounting strength and poor heat radiation characteristics. The fourth problem is that relatively large spacing has to be provided between the individual semiconductor chips for the mounting process, whereby the dielectric substrate requires a large area. Moreover, since such large spacing is provided between the semiconductor chips, the inductance between grounding terminals of each active element increases, whereby the operation of the element becomes unstable.
For MMIC, the first problem is that since the active element and the passive elements are designed and produced on the same semiconductor chip, any design change requires reproduction of the whole device, thereby requiring a long time for the device development. The second problem is that the specific resistance of the semiconductor substrate is smaller than that of the dielectric substrate, and a high Q value cannot be obtained, whereby it is difficult to produce a high-performance passive element. In particular, since the semiconductor substrate has a smaller resistance than that of the dielectric substrate, a passive circuit produced on the semiconductor substrate may suffer from characteristic deterioration due to factors such as leakage of a signal to the substrate. The third problem is that the passive elements occupy a major area of the semiconductor chip, thereby increasing the material cost The fourth problem is that the active element and the passive elements are integrated on the same semiconductor chip with a high density, thereby resulting in a poor electrical isolation characteristic between the respective elements.
Thus, while the HMIC technique and the MMIC technique have some advantages, they also have shortcomings to be overcome.
A microwave and millimeter wave device of the present invention includes: a dielectric substrate including at least one signal line, a passive circuit and a first grounding conductor portion which are formed on a surface side of the dielectric substrate; and a semiconductor substrate including a plurality of active elements. The signal line is physically and electrically connected to an input/output terminal of the active element via a metal bump; and the first grounding conductor portion is physically and electrically connected to a grounding terminal of the active element via another metal bump.
In one embodiment, the microwave and millimeter wave device further includes a second grounding portion on a surface side of the semiconductor substrate, wherein the second grounding portion is formed by connecting respective grounding terminals of the plurality of active elements to one another via a first conductor.
In one embodiment, a second conductor is provided on a reverse side of the semiconductor substrate; and the grounding conductor portion on the surface side of the semiconductor substrate is connected to the second conductor via a through hole.
In one embodiment, a grounding conductor surface is provided on a reverse side of the dielectric substrate; and the grounding conductor surface is connected to the grounding conductor portion on the surface side of the dielectric substrate via a through hole.
In one embodiment, the dielectric substrate includes a first dielectric layer, an intermediate conductor layer and a second dielectric layer; a grounding conductor surface is provided on a reverse side of the second dielectric layer; a ground conductor portion is provided on the surface side of the dielectric substrate; and through holes are provided to connect between the grounding conductor portion and the intermediate conductor layer and between the intermediate layer and the grounding conductor surface, respectively.
In one embodiment, the intermediate conductor layer includes a slot coupling hole; a second signal line is provided on a reverse side of the second dielectric layer; a first signal line is provided on a surface side of the first dielectric layer; and the second signal line is electromagnetically coupled, for a desired frequency, to the first signal line via the slot coupling hole.
In one embodiment, at least a mixer input matching circuit and a filtering circuit are provided as the passive circuits; and the microwave and millimeter wave device further comprises a frequency conversion device.
In one embodiment, a frame body is provided along a periphery of the dielectric substrate; a lid is provided on the frame body so as to cover the semiconductor substrate; and the frame body and the lid are respectively grounded.
In one embodiment, a first signal line is provided on the surface side of the dielectric substrate; an external connection terminal and a second signal line are provided on a reverse side of the dielectric substrate; the external connection terminal is connected to the second signal line; the second signal line is connected to the first signal line via a through hole or a slit coupling hole; and the first signal line is connected to the passive circuit.
In one embodiment, an input terminal is provided on the surface side of the dielectric substrate; a planar antenna is provided on a reverse side of the dielectric substrate; the planar antenna includes a power supply portion for connection to the surface side of the dielectric substrate; the power supply portion is connected to the input terminal via through hole or a slot coupling hole; and an input is provided from the input terminal to the passive circuit.
The dielectric substrate may be made of silicon having an insulation film on the surface side of the dielectric substrate; and the passive circuit is formed by a semiconductor process for the silicon.
According to another aspect of the present invention, a microwave and millimeter wave device includes: a dielectric substrate including at least one signal line, a passive circuit and a grounding conductor portion which are formed o a surface of the dielectric substrate; and a semiconductor substrate including a plurality of transistors, a diode, and function block constituted by a predetermined circuit element, wherein the dielectric substrate and the semiconductor substrate are physically and electrically connected to each other via a metal bump.
The metal bump may allow connection between terminals provided on the dielectric substrate and the semiconductor substrate.
The dielectric substrate may be a multilayered thin film substrate provided over the semiconductor substrate.
The function block may include a pair of transistors and a pair of diodes.
The function block may include a transistor and a bias circuit for the transistor.
The function block may include a transistor and a feedback circuit for the transistor.
Grounding terminals for the function block and the respective transistors may be provided on the dielectric substrate at such positions as to surround the function block and the transistors.
Alternatively, grounding terminals for the function block and the respective transistors may be provided on the semiconductor substrate at such positions as to surround the function block and the transistors.
Furthermore, grounding terminals for the function block and the respective transistors may be provided on at least one of the dielectric substrate and the semiconductor substrate at such positions as to surround the function block and the transistors.
In one embodiment, the plurality of transistors are arranged to form first and second rows, wherein input and output terminals for the first row are provided on the semiconductor substrate along a first direction while input and output terminals for the second row are provided on the semiconductor substrate along a second direction which is substantially opposite to the first direction.
Thus, the invention described herein makes possible the advantage of providing a small, low-cost microwave and millimeter wave device which allows the development time to be shortened, improves the mounting strength of a semiconductor chip and has good passive element characteristics.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.